The present invention relates to a new and improved torpedo and a method by which engine exhaust gas is stored as the torpedo is discharged from a torpedo tube.
Known torpedos commonly have engines which are driven by a supply of gas under pressure, such as steam or gas generated from a liquid or solid monopropellant fuel. During operation of the engine, there is a continuous flow of the gas through the engine. The engine exhaust gas has previously been discharged through hollow drive shafts connected with torpedo drive propellers. Such a torpedo drive arrangement is disclosed in U.S. Pat. No. 3,151,527.
In addition, it has been suggested that the flow of gas which is discharged from a torpedo drive engine could be exhausted through an outer wall of the torpedo in the manner disclosed in U.S. Pat. No. 3,048,137. This patent contemplates that the exhaust gas will be conducted from the engine to an exhaust gas expansion chamber having porous or foraminous walls. The exhaust gas discharged from the expansion chamber flows through the foraminous wall into the water around the torpedo. The openings in the expansion chamber wall are sized so that exhaust gas passes through the expansion chamber wall at a low velocity and in minute bubbles.
A torpedo drive system in which the products of combustion flow through an annular space or tank is disclosed in U.S. Pat. No. 3,109,401. Exhaust gas flows from the storage space through a plurality of open holes or apertures formed in the housing or hull of the torpedo. Although there is a free flow of exhaust gas from the annular storage space through open holes, a pressure regulating and uni-directional flow valve is provided to maintain the combustion chamber at a desired pressure and to prevent an inflow of water when the combustion chamber is below the desired pressure.
During operation of the engines in these known torpedos, there is a continuous flow of exhaust gas from the torpedos. If an attempt was made to operate the torpedo drive engine when the torpedo is in a torpedo tube, the exhaust gases would accumulate at the inner end of the tube so that the torpedo drive propellers would be surrounded by exhaust gas. Since the drive propellers are designed to drive the torpedo under water, their performance is greatly impaired when the propellers are located in a bubble of exhaust gas.
The problem with accumulation of exhaust gases at one end of a torpedo tube during operation of the torpedo drive engine has been overcome in the past by using compressed air to discharge the torpedo from the torpedo tube. Thus with known torpedos having drive engines which continuously exhaust gas, compressed air has been used to blow the torpedo out of the torpedo tube. Once the torpedo has moved clear of the torpedo tube, the torpedo drive engines are started and exhaust gases are discharged from the torpedo. However, as the torpedo is discharged from the torpedo tube, a large bubble of compressed air escapes from the torpedo tube. This bubble of compressed air is relatively easy to detect.
Other known torpedos have had electric drive systems. With electric drive systems, there are no exhaust gases to be discharged from the torpedo. Therefore, the electric torpedo drive motors can be started in the torpedo tube. The torpedo swims out of the torpedo tube rather than being blown out of the torpedo tube by compressed air. Since compressed air is not used to discharge the torpedo from the torpedo tube, an easily detected bubble of compressed air is not discharged from the torpedo tube as an electrically driven torpedo is launched. While electrically driven torpedos have the advantage of being operable without compressed air to launch them from a torpedo tube, the electric drive systems with their associated batteries have limited performance capabilities. Due to these limited performance capabilities, it is often preferred to use torpedos having gas driven engines even though they must be discharged from a torpedo tube before the engines are started.